The present invention relates to piston and slipper arrangements used in hydraulic pumps, and more particularly, to an improved slipper which prevents harmful contaminants from being embedded in the surface of the seat between the piston and slipper.
It is conventional to provide a hydraulic pump including a plurality of radially reciprocating pistons having enlarged spherical ends and slippers that are articulately mounted on the spherical ends of the pistons. The slippers engage a cam surface on a cam or reaction member of a rotatable drive shaft. One typical slipper design includes a dished thrust surface in the shape of a truncated cone which is in engagement with the spherical head of a respective piston. The rotative force of the drive shaft is transmitted through the slippers to cause the pistons to reciprocate.
A problem with known piston-slipper arrangements is that there are crevices formed adjacent the contact area between the spherical end of the piston and the dished thrust surface of the slipper which permit contaminants to lodge or jam. As relative motion occurs between the piston end and slipper, the contaminants can enter between the contact surfaces, thereby spoiling the seat.
Thus, there has been a need for an improved slipper which prevents harmful contaminants from being embedded in the surface of the seat between the piston and slipper. The disadvantages of present piston and slipper arrangements have resulted in the slipper of the present invention which effectively eliminates the potential for contaminants to enter the contact surface between the piston and slipper with resultant spoiling of the seat.